﻿// 斐波那契递归数列

#include <iostream>
using namespace std;
long long int F(long long int x) 
{
	if (x == 1 || x == 2)
	{
		return 1;
	}
	else
	{
		return (F( x-1)+ F(x - 2));
	}
}
int main()
{
	long long int x;
	cin >> x;
	
    cout << F(x);
}

